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Sgr B2 hard X-ray emission with INTEGRAL after 2009: still detectable?

Abstract : The molecular cloud Sgr B2 is a natural Compton mirror in the Central Molecular Zone. It is believed that the observed fading of the Sgr B2 X-ray emission in continuum and the Fe Kα 6.4 keV line indicates past X-ray flare activity of the supermassive black hole Sgr A. Sgr B2 was investigated by the INTEGRAL observatory in the hard X-ray in 2003-2009, showing clear decay of its hard X-ray emission. In this work, we present a long-term time evolution of the Sgr B2 hard X-ray continuum after 2009, associated with the hard X-ray source IGR J17475-2822 as observed by INTEGRAL. The 30-80 keV sky maps, obtained in 2009-2019, demonstrate a significant excess spatially consistent with IGR J17475-2822. The observed 2003-2019 light curve of IGR J17475-2822 is characterized by a linear decrease by a factor of ~2 until 2011, after which it reaches a constant level of ~1 mCrab. The source spectrum above 17 keV is consistent with a power-law model with Γ = 1.4 and a high-energy cut-off at ~43 keV. The Sgr B2 residual emission after ~2011 shows a good correspondence with models of X-ray emission due to the irradiation of the molecular gas by hard X-rays and low-energy cosmic ray ions. We discuss the possible origin of the residual Sgr B2 emission after 2011 within these models, including theoretically predicted multiply scattered emission.
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Contributor : Nathalie POTHIER Connect in order to contact the contributor
Submitted on : Monday, June 27, 2022 - 9:06:46 AM
Last modification on : Wednesday, June 29, 2022 - 3:09:32 AM

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Ekaterina Kuznetsova, Roman Krivonos, Alexander Lutovinov, Maïca Clavel. Sgr B2 hard X-ray emission with INTEGRAL after 2009: still detectable?. Monthly Notices of the Royal Astronomical Society, 2022, 509, pp.1605-1613. ⟨10.1093/mnras/stab3004⟩. ⟨insu-03705390⟩



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